This invention relates to valve actuators and methods of controlling valves. Embodiments of the present invention pertain to valve actuators for fluid drain valves used in industrial washing machines and other applications with high volume drain flow. Embodiments of the present invention also pertain to methods of controlling high volume drain valves, such as drain valves for industrial washing machines. Although embodiments of the present invention are described as drain valve actuators and related methods, the present invention is not limited to drain valve applications and can be practiced in embodiments applied to valves other than drain valves.
An existing industrial washing machine drain valve actuator has a motor which closes the drain valve against a force of a coil spring which is attached to the output shaft of the motor. The coil spring applies a force to the drain valve in the drain valve open direction. The motor is an AC shaded pole geared motor which closes the drain valve against the coil spring when AC voltage is applied to the motor winding. The AC power is provided to the motor as long as the valve must remain in the closed position. When the AC power is removed from the motor the coil spring forces the drain valve into the open position. A portion of the torque that the geared motor develops is used to place the coil spring in tension. The rest of the torque is used to move the drain valve to the closed position and to maintain the valve in the closed position. The locked rotor torque of the geared motor is enough to overcome the coil spring tension and to keep the valve sealed closed. When the AC voltage is removed from the motor terminals the coil spring recoils and the mechanical energy stored in the spring transfers to a rotary motion which opens the valve.
Existing drain valves can be improved. For example, the drain valve has hard mechanical stops at both end points of the closed position and the opened position. In other words, the coil spring forces the drain valve open until the moving valve hits a hard mechanical stop and cannot be moved any further. Similarly, the motor forces the drain valve closed until the moving valve hits a hard mechanical stop and cannot be moved any further.
Another problem with existing drain valve actuators is that the shaded pole geared motor stays on continuously during the time the valve is closed. The motor continuously consumes electrical energy which is needed to overcome the tension of the spring and to keep the valve closed.
Examples of drain valve actuators can be found in U.S. Pat. No. 6,186,471, U.S. Pat. No. 6,250,323, U.S. Pat. No. 6,290,207 and U.S. Pat. No. 6,371,440. The present invention has improvements over such drain valve actuators.
Accordingly, needs exist to improve valve actuators and related methods, such as drain valve actuators and related methods, for the reasons mentioned above and for other reasons.